On the panel, the cast avoided giving any actual spoilers for what's coming up — but there were tons of hilarious and touching moments. Matt Smith was full of genuine gratitude for the fans' enthusiasm, doing an "I'm not worthy" bow to the crowd as everyone clapped.

And Karen Gillan did let slip that Amy has a huge secret, which nobody knows yet. Steven Moffat has told it to her, but she hasn't shared it with anyone else. Not even Matt Smith, who seemed genuinely frustrated. "She won't tell me!" He did pantomime fists. "I feel so powerful right now," laughed Gillan. "This never happens."

There was much talk about the shocking revelation that River Song is Amy Pond's daughter — the cast didn't even know until after the readthrough for the episode. They had a script with a dummy ending, and then Moffat took Smith and Gillan aside and told them the real ending — which astonished them. Only Alex Kingston had known the truth about River Song, for months — in keeping with Moffat's penchant for telling a cast member a secret that nobody else is allowed to have. (Although Whithouse said he knew River's secret months in advance, because it's referenced with one line in "The God Complex.")

There will be "huge cliffhangers" being resolved in the upcoming episodes, said Smith. Episode ten will explore something of the Doctor's dark side, said Amy, and we'll explore the idea that "the Doctor lies." There was a lot of talk about the Doctor's dark side — Smith said he'd like to see the Dream Lord again, preferably with a huge army at his back, and he believes the Doctor "has a lot of blood on his hands." He's responsible for a lot of death, and he's lost a lot of people, and if the Doctor ever stopped being bubbly and effervescent and rushing around and saving people all the time — if the Doctor actually stopped and sat down — he would be overwhelmed by the darkness.

Toby Whithouse (Being Human) explained the secrets of writing monsters: You need to find the humanity in the monster, and a believable motivation. He felt like Rosanna in "The Vampires of Venice" had a great motivation — she wanted to save her people, and she just wanted to take a small piece of the Earth to do it. He always wants his monsters to have a believable motivation. The show, at its heart, is a mystery show, where the Doctor tries to figure the monster out — and that includes understanding what makes the monster tick. And the Doctor never approaches the monster with the aim of killing it.

More stuff from the panel:

Matt Smith reiterated his favorite Doctor is Patrick Troughton, but there was also a lot of love for Tom Baker.

Matt Smith was given a TARDIS manual on his first day on set, showing him how to fly the TARDIS — he always uses the same switches every time, including pulling the big gear and the big lever with the lights on it, and then typing in his destination on the big keyboard.

Smith would like the show to cross over with True Blood. Gillan would like the show to cross over with Star Trek: The Next Generation. (She just met Brent Spiner and was star-struck.) And Smith would love to do a cameo on The Big Bang Theory, a show which references Doctor Who often.

Also, Smith would love to have either J.J. Abrams or Edgar Wright to write for the show. Karen Gillan and Toby Whithouse would like Roald Dahl to write an episode. (Time travel would have to be involved, of course.)

Oh, and Smith said that Moffat just gave him a fez because he kept "bleating on" about wanting the Doctor to have a hat — so Moffat gave the Doctor the stupidest hat he could think of. And now everybody loves it. But Smith hinted that the Doctor's stetson would be playing an important role in the upcoming episodes.